It seems that the 34mm restrictor can make a huge difference - https://www.ewrc-results.com/results...2023/?s=427051

Vaidotas Žala was driving a R5 Skoda with a 34mm restrictor and in the end he was almost a minute faster than everyone else. He's a very fast driver, but I think that the 34mm restrictor also helped quite a bit and the competition was also not slow.